Hi,
An electronic engineer at our field really likes these batteries for his big gassers. He uses them on the RX and ignition. He keeps track of the MaH on each recharge/discharge. This is the only way to tell how much flight time a pack has. As said before these packs have a very flat voltage curve. A volt meter MAY not be a safe measure depending on the power requirements of the given plane. Timing the recharge if you can't measure Mah. Keep a record.